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Posted to issues@madlib.apache.org by "Frank McQuillan (JIRA)" <ji...@apache.org> on 2018/08/10 15:12:00 UTC
[jira] [Comment Edited] (MADLIB-1270) Unexepcted behavior in
vec2cols function
[ https://issues.apache.org/jira/browse/MADLIB-1270?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16575589#comment-16575589 ]
Frank McQuillan edited comment on MADLIB-1270 at 8/10/18 3:11 PM:
------------------------------------------------------------------
Here is one possible approach:
* Use the max array length to determine the number of columns
* It means some of the generated rows may have NULLs if the array for a particular row is smaller than the max.
* If the optional column_names parameter is used and the number of elements does not match, then throw an error.
was (Author: fmcquillan):
Here is one possible approach:
{code}
IF
feature_names is specified
THEN
make the number of columns equal to the size of the feature_names array
ELSE IF
feature_names is not specified
THEN
make the number of columns equal to the max size of the array in vector_col
{code}
In all cases above, some of the generated rows may have NULLs if the array for a particular row is smaller.
> Unexepcted behavior in vec2cols function
> ----------------------------------------
>
> Key: MADLIB-1270
> URL: https://issues.apache.org/jira/browse/MADLIB-1270
> Project: Apache MADlib
> Issue Type: Bug
> Components: Module: Utilities
> Reporter: Rashmi Raghu
> Priority: Minor
> Fix For: v1.15.1
>
>
> There is some unexpected behavior when vector column to be split contains different numbers of elements in the vectors. E.g.
> Input table:
> select * from test order by id;
> id | t
> ----+---------
> 1 | \{a,b}
> 2 | \{c,d}
> 3 | \{e,f}
> 4 | \{g,h,i}
> 5 | \{j}
> (5 rows)
>
> select madlib.vec2cols('test','test_out_5','t',array['c1','c2','c3'],'id');
> ERROR: plpy.Error: vec2cols: Mismatch between size of vector_col and number of cols in feature_names.
> CONTEXT: Traceback (most recent call last):
> PL/Python function "vec2cols", line 23, in <module>
> return vec2cols_obj.vec2cols(**globals())
> PL/Python function "vec2cols", line 149, in vec2cols
> PL/Python function "vec2cols", line 112, in get_names_for_split_output_cols
> PL/Python function "vec2cols", line 77, in _assert
> PL/Python function "vec2cols"
>
> select madlib.vec2cols('test','test_out_5','t',array['c1','c2'],'id');
> vec2cols
> ----------
> (1 row)
> select * from test_out_5 order by id;
> id | c1 | c2
> ----++--------
> 1 | a | b
> 2 | c | d
> 3 | e | f
> 4 | g | h
> 5 | j |
> (5 rows)
>
>
> select madlib.vec2cols('test','test_out_6','t',array['c1'],'id');
> ERROR: plpy.Error: vec2cols: Mismatch between size of vector_col and number of cols in feature_names.
> CONTEXT: Traceback (most recent call last):
> PL/Python function "vec2cols", line 23, in <module>
> return vec2cols_obj.vec2cols(**globals())
> PL/Python function "vec2cols", line 149, in vec2cols
> PL/Python function "vec2cols", line 112, in get_names_for_split_output_cols
> PL/Python function "vec2cols", line 77, in _assert
> PL/Python function "vec2cols"
>
> --- Update-----
> There are a couple of decisions to be made regarding supporting arrays of different lengths:
> -If we choose the array with maximal length in the vector_col, what do we do if the user's passed-in feature_names does not have the same number of elements?
> -What are the performance issues with looking through our vector_col for the array with maximal length?
> -How will we handle default feature names: will we create a feature name for every element of the longest array entry?
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